The present application is based upon the one identified below, and the contents thereof are incorporated herein by reference:
Japanese Patent Application Heisei 10 No. 97595 (filed upon April 9th, Heisei 10).
1. Field of the Invention
The present invention relates to a vibration cancellation apparatus and to an exposure apparatus, and more particularly relates to a vibration cancellation apparatus and to an exposure apparatus which, based upon vibration which is detected, reduce the above-described vibration by driving a weight in a direction to quell it.
2. Related Art
In accompaniment with enhancement of the accuracy of precision equipment such as step-and-repeat type and step-and-scan and-scan type exposure apparatus and the like, the requirement has arisen for isolating minute vibrations at the micro-G level which act upon a base table (a vibration cancellation table) from the surface of a foundation floor on which a precision equipment is set. For this reason, there have been many proposals to support the vibration cancellation table by vibration cancellation pads, so as to isolate vibrations from the surface of the foundation floor. Various types of vibration cancellation pads have been used to support the vibration cancellation tables of vibration cancellation apparatus, such as mechanical dampers containing compression coil springs in damping fluid and air type dampers or the like. In particular, air spring vibration cancellation apparatus equipped with air type dampers are widely used for supporting precision equipment, because it is possible to set the spring constant low so as to isolate vibrations above about 10 Hz. Further, active vibration cancellation apparatus have recently been proposed in order to defeat the limitations of prior art passive vibration cancellation apparatus (for example, refer to Japanese Patent Laying Open Publication Heisei 8-166043 filed by the same applicant as the present application). These are vibration cancellation apparatus which perform vibration control by detecting vibration of the vibration cancellation table by a sensor and by driving an actuator based upon the output of this sensor, and theoretically they are endowed with a vibration isolation efficacy which exhibits no resonant peaks in the low frequency control band.
The use of a reaction frame has been practiced as one means for yet further enhancement of the vibration cancellation performance of the above-described active vibration cancellation apparatus. Such a reaction frame will now be explained. A mask stage or a substrate stage is set up upon the vibration cancellation table of the above-explained exposure apparatus. During exposure action, in accompaniment with repeated acceleration and deceleration of the mask stage or the substrate stage (hereinafter termed the moving stage), vibration increasing forces act upon the vibration cancellation table due to reactions received from the moving stage. An element used for preventing this vibration increasing forces from acting upon the vibration cancellation table is a reaction frame.
That is, the reaction frame is fixedly provided upon the surface of the foundation floor on which the exposure apparatus is installed, and this reaction frame receives the reactions which accompany acceleration and deceleration of the moving stage. Accordingly, the above-described reactions which are transmitted to the reaction frame are not transmitted to the vibration cancellation table, but are transmitted to the surface of the foundation floor. By doing this, it is possible to prevent vibration of the vibration cancellation table in accompaniment with acceleration and deceleration of the moving stage.
Further, with the above described exposure apparatus, it has been proposed to set up the illumination optical system and the exposure apparatus main body as separate units (for example, in Japanese Patent Application Heisei 9-310438 filed by the same applicant as the present application). Such an arrangement is for preventing vibration generated during the scanning exposure action of a step-and-scan exposure apparatus when the reticle blind which intercepts light outside the exposure range upon the reticle pattern moves synchronously with scanning exposure from being transmitted to the exposure apparatus main body. With the above described step-and-scan exposure apparatus, the exposure apparatus main body and the illumination optical system are mutually separately provided and each of them is supported by an active vibration cancellation apparatus, and vibration cancellation action is performed independently for each of them while their relative position is maintained. By doing this, along with it being possible to prevent vibration generated as described above in the illumination optical system from being transmitted to the exposure apparatus main body, it is also possible to maintain the accuracy of relative position determination between the illumination optical system and the exposure apparatus main body, as is desirable.
However, along with the increase in accuracy of position determination of the moving stage which is being required, it has become impossible to ignore vibration set up in the reaction frame itself. That is to say, the reaction frame receives the reactions generated accompanying acceleration and deceleration of the moving stage. Vibration is set up in the reaction frame when it experiences these reactions. And vibration of the reaction frame is transmitted through the surface of the foundation floor on which the exposure apparatus is installed to the exposure apparatus main body.
As an accuracy of position determination of the moving stage becomes high, it has become impossible to ignore vibration transmitted to the exposure apparatus main body.
Further, with an apparatus in which the illumination optical system and the exposure apparatus main body are set up as separate units, there have been demands for further suppression of vibration generated within the illumination optical system, in order to enhance the performance of position determination of the illumination optical system and the exposure apparatus. The reason for this is that vibration generated within the illumination optical system is also transmitted to the exposure apparatus main body via the surface of the foundation floor as well.
Yet further, when a stage or the like operates within the exposure apparatus main body, it may happen that residual vibration which has not been eliminated by the reaction frame generates undesirable vibration in the projection optical system. When this happens, exposure action cannot be performed until the vibration of the projection optical system has been abated to a specified level, and sometimes this leads to deterioration of the throughput of the exposure apparatus.
The above problems due to vibration can occur not only with an exposure apparatus, but also with a precision tool machine or a precision measuring device or the like as well. That is to say, it can happen that vibration set up within a precision tool machine or a precision measuring device, or vibration transmitted from the outside, can deteriorate the processing accuracy in the case of a precision tool machine, or the measurement accuracy in the case of a precision measuring device.
A first objective of the present invention is to enhance the throughput of an exposure apparatus and the accuracy of positional determination for a moving stage thereof, by suppressing vibration set up in a reaction frame.
A second objective of the present invention is to enhance the accuracy of relative position determination between an exposure apparatus main body and an illumination optical system which are provided as mutually separate units, by suppressing vibration set up due to movement of a movable element housed in the illumination optical system.
A third objective of the present invention is to propose a vibration cancellation apparatus which can be provided to a device etc. for which reduction of vibration is called for, such as a precision tool machine or a precision measuring device or the like.
In order to attain the above described objectives, the vibration cancellation apparatus according to this invention comprises: a base member; a movable element which is set up upon the base member, and is movable upon the base member; a reaction transmission member which discharges reaction generated when the movable element moves upon the base member by transmitting it to a surface of a foundation floor of the base member; a vibration detection device which detects vibration generated in the reaction transmission member; a weight which is movable in a direction to reduce the vibration, and which is provided to the reaction transmission member; and a vibration cancellation drive device which drives the weight so as to reduce the vibration, based upon the vibration detected by the vibration detection device.
According to this invention, when reaction generated when the movable element which is movable on the vibration cancellation table is driven is transmitted via the reaction transmission member to the surface of the foundation floor, it is possible to reduce the vibration set up in the reaction transmission member over a short time period by detecting vibration which is set up in the reaction transmission member to drive the weight so as to decrease this vibration. By doing this, it also becomes possible to suppress over a short time period vibration of the vibration cancellation table generated by vibration in the reaction transmission member being transmitted to the vibration cancellation table.
The present invention can also be applied to an exposure apparatus which projects a pattern formed on a mask substrate via a projection optical system onto a substrate upon a substrate stage. And the exposure apparatus according to this invention comprises the vibration cancellation apparatus including a base member; a movable element which is set up upon the base member, and is movable upon the base member; a reaction transmission member which discharges reaction generated when the movable element moves upon the base member by transmitting it to a surface of a foundation floor of the base member; a vibration detection device which detects vibration generated in the reaction transmission member; a weight which is movable in a direction to reduce the vibration, and which is provided to the reaction transmission member; and a vibration cancellation drive device which drives the weight so as to reduce the vibration, based upon the vibration detected by the vibration detection device. According to this invention, over a short time period it is possible to reduce undesirable vibration of the exposure apparatus main body generated by vibration of the reaction transmission member being transmitted. By doing this, it becomes possible to enhance the throughput of the exposure apparatus.
Further, the exposure apparatus according to this invention may include a mask stage; a substrate stage; an exposure apparatus main body which includes a projection optical system which projects a pattern image on a mask substrate which is set up on the mask stage upon a substrate which is set up on the substrate stage; an illumination unit for shining illumination light upon the mask substrate, set up upon the surface of the foundation floor of the exposure apparatus main body as a separate unit from the exposure apparatus main body; a vibration detection device which detects vibration generated in the illumination unit; a weight which is movable in a direction to reduce the vibration, and which is provided to the illumination unit; and a vibration cancellation drive device which drives the weight so as to reduce the above described vibration, based upon the vibration detected by the vibration detection device. According to this invention, it is possible to suppress undesirable vibration by detecting vibration set up in the illumination unit, and by driving the weight so as to reduce this vibration. By doing this, it becomes possible to maintain the accuracy of relative positional determination between the illumination unit and the exposure apparatus main body.
Further, the present invention may be applied to a vibration cancellation apparatus which includes a vibration detection device which is provided to a vibration cancellation object, and which outputs a vibration signal according to the magnitude of vibration generated in the vibration cancellation object; a weight which is provided so as to be capable of relative movement with respect to the vibration cancellation object; a drive device which generates relative movement between the weight and the vibration cancellation object; and a position determination device which determines the position of the weight and outputs a position signal according to the position of the weight. And the drive device performs control based upon a first control loop which controls the drive speed of the weight based upon the vibration signal, and a second control loop which moves the weight to a specified position based upon the position information.
According to this invention, by having a control loop in which the position of the weight is shifted to a specified position based upon a position signal output from the position detection device of value according to the position of the weight, it becomes possible to drive this weight while leading it to the specified position. Accordingly, it becomes possible to prevent the impropriety of the weight undesirably becoming gradually displaced from its specified position while being driven, and as a result the weight undesirably arriving outside of its range of movement.
Further, the vibration cancellation apparatus according to the present invention may further include a control device which controls the drive device based upon the first control loop and the second control loop; and this control device may include a first filter device which reduces intensity of the vibration signal with respect to a frequency component outside a predetermined band, and a second filter device which reduces intensity of the position signal with respect to a frequency component outside a predetermined band. In this vibration cancellation apparatus, the drive device is controlled so as to reduce the vibration by performing the first control loop based upon the vibration signal which has been filtered by the first filter device, and by performing the second control loop based upon the position signal which has been filtered by the second filter device.
According to this invention, it is possible to drive the weight based upon the frequency components of the signals which are required for reducing the vibration of the vibration cancellation object, by reducing the signal intensity outside previously determined frequency bands by the first and second filter devices. Due to this, the inconvenience of generation of undesirable vibration in the vibration cancellation object is prevented by quelling only vibrations of the frequency components which are substantially suitable for vibration cancellation.
Furthermore, with regard to the second control loop, this second control loop may set the drive speed of the weight so as not to generate new vibration in the vibration cancellation object when the drive device is driving the weight based upon the second control loop. By doing this, it becomes possible to suppress the generation of undesirable vibrations when the drive device is driving the weight.
Further, with the vibration cancellation apparatus according to the present invention, the mass of the weight may also be adjustable. By making the mass of the weight adjustable in this manner, it becomes possible to adjust the mass of the weight according to the magnitude of the vibrations set up in the vibration cancellation object, and according to the mass of the vibration cancellation object.
Yet further, in the vibration cancellation apparatus according to the present invention, the drive device may also be a linear motor. By constructing the drive device as a linear motor, it is possible to suppress the generation of undesirable new vibration during vibration cancellation, since it is possible to suppress the generation of the undesirable reactions (moments) in the rotational direction which are generated when, for example, a rotational type motor starts, accelerates, decelerates, and stops.
Furthermore, in the vibration cancellation apparatus according to the present invention, it is desirable that, in the linear motor, a coil should be disposed in a fixed section side, while a moving magnet and the weight are disposed in a movable section side. By disposing the coil on the fixed section side in this manner, it is possible to reduce the mass of the weight, since it is possible to drive the moving magnet which has a mass which is great compared to that of the coil together with the weight. Accordingly it is possible to reduce the size and weight of the vibration cancellation apparatus as a whole. Further, by disposing the coil on the fixed section side, it also becomes difficult for problems such as breaking of the wires and the like to occur, since it cannot happen for the cables for supplying electrical power to the coil to become slackened or stretched.
Yet further, the vibration cancellation apparatus according to the present invention may include a first vibration detection device which is provided to a vibration cancellation object, and which outputs a first vibration signal according to the magnitude of vibration generated in the vibration cancellation object; a weight which is provided so as to be capable of relative movement with respect to the vibration cancellation object; a second vibration detection device which is provided to the weight, and which outputs a second vibration signal according to the magnitude of vibration generated in the weight; and a drive device which generates drive force which causes relative movement between the weight and the vibration cancellation object; and the drive device may perform control based upon the first vibration signal and the second vibration signal.
According to this invention, it is possible to maintain a predetermined state of coupled vibration between the vibration system which includes the weight and the vibration system which includes the vibration cancellation object by using the first vibration signal which is output from the first vibration detection device and the second vibration signal which is output from the second vibration detection device. By doing this it is possible to reduce the peak value of the vibration, and thereby it becomes possible to quell the vibration quickly.
The vibration cancellation apparatus according to this invention may further include a resilient member which is connected in parallel equivalently to the drive device between the vibration cancellation object and the weight. Also by further providing the resilience member connected in parallel equivalently to the drive device in this manner, it is possible to maintain a predetermined state of coupled vibration between the vibration system which includes the weight and the vibration system which includes the vibration cancellation object. By doing this it is possible to reduce the peak value of the vibration, and thereby it becomes possible to quell the vibration quickly.
Yet furthermore, the present invention may be a vibration cancellation apparatus for reducing vibration generated in a vibration cancellation object, and may include a vibration detection device which outputs a vibration signal according to the magnitude of vibration generated in the vibration cancellation object; a drive device which generates a drive force to reduce the vibration, based upon the vibration signal; a support member which supports the vibration detection device and the drive device; and a fixing device which fixes the support member to the vibration cancellation object in a removable manner. According to this type of structure, it becomes easy to fix the vibration cancellation apparatus to the vibration cancellation object, and to detach it therefrom.
In the vibration cancellation apparatus according to this invention, the support member may be a casing member which houses the vibration detection device and the drive device in its interior. In this manner, by making the support member as a casing member which houses the vibration detection device and the drive device in its interior, improvement of the compactness and unitary construction of the vibration cancellation apparatus become easy, and it is possible easily to fit and to detach the vibration cancellation apparatus to and from the subject for vibration control or vibration cancellation countermeasures.
Finally, the present invention may be applied to an exposure apparatus in which a predetermined image is formed upon a substrate which is mounted upon a substrate stage, equipped with any one of the vibration cancellation apparatus described above. According to this kind of exposure apparatus, it becomes possible to quell vibration which is generated in the exposure apparatus very quickly. As a result, it becomes possible to enhance the throughput of the exposure apparatus. Furthermore, by also making it possible to reduce vibration during exposure action, it becomes possible to enhance the accuracy of the pattern which is formed upon the substrate.